CRISPR-edited donor cells show promise for safer blood cancer transplants

In a multicenter phase 1/2 study, investigators applied CRISPR-Cas9 to eliminate the CD33 antigen from allogeneic stem cells before transplanting them into adults with high-risk AML or MDS. The edited product, named trem-cel, was supplied by Vor Biopharma and administered at 30 transplant sites across the United States and Canada. Following transplantation, patients received maintenance therapy with gemtuzumab ozogamicin, an antibody that binds CD33 and delivers a cytotoxic payload.

The gene-edited cells successfully engrafted and produced normal blood lineages, and patients maintained adequate blood counts during the antibody treatment. A single case report within the trial showed that a patient who later relapsed could be treated with donor-derived CD33-targeted CAR-T cells and achieved durable remission. The findings provide a proof-of-concept that removing CD33 from donor cells may allow more aggressive CD33-directed therapies while preserving healthy hematopoiesis.